BOGOTA, Colombia – Human Rights Watch says Colombia has "chronically failed" to protect people trying to reclaim stolen land and that threatens to sabotage President Juan Manuel Santos' unprecedented efforts to end the Western Hemisphere's worst internal refugee problem.

The organization says in a report published Tuesday that fewer than 1 percent of criminal investigations into forced displacements have yielded convictions. And it counts at least 21 land claimant activists killed since 2008.

Land restoration is at the heart of Colombia's half-century-old internal conflict. Human Rights Watch says some 4.5 million people have been forced from their land, chiefly by far-right militias working for ranchers and agro-businessmen.

Those militias demobilized during the 2002-2010 presidency of Alvaro Uribe but have regrouped and are now called "emerging criminal bands."